The present invention generally relates to vital sign monitors for detecting physiological parameters such as heartbeat, respiration, physical movement, blood pressure and other bodily activities of a patient for use in a magnetic resonance imaging (MRI) environment, confined care facilities (e.g., geriatrics) and in-hospital during surgery, postoperative recovery and intensive care units.
1. Background of Vital Sign Monitoring in Magnetic Resonance Imaging Labs
Use of Magnetic Resonance Imaging (MRI) is rapidly growing in the U.S. and other parts of the world for investigations and diagnosis of many diseases. Statistical data published by In-vivo Research shows that over 18 million scans are performed per year in the U.S. alone. To better understand the problems of monitoring patients undergoing MRI scanning, a summary of the key steps required in generating a patient""s image is provided:
1. A strong magnetic field, on the order of 1.5 to 2 Teslas (1 Tesla=10,000 Gauss, earth""s magnetic field is 1 Gauss), is required to align all randomly oriented nuclei cells of the patient;
2. Radio frequency (RF) pulses, directed at the patient, are used in the presence of the external magnetic field, to cause the cell nuclei to absorb more energy producing magnetic resonance. This is generally referred to as super charging of the nuclei, which further changes their alignment from the original state;
3. The RF supercharged cell nuclei recover their original state of alignment within the magnetic field by re-emitting the absorbed RF energy. The RF signal re-emitted by each tissue is proportional to the difference between the energized magnetic resonance states and the original alignment states. Tissue imaging contrast develops as a result of the different rates of realignment;
4. Time varied magnetic field (TVMF) gradients are applied briefly to spatially encode the RF signals emitted from the patient tissues;
5. The RF coils in the MRI pick up these spatially encoded RF signals emitted from the tissues and are transformed by a computer into 2 or 3 dimensional images.
The strong magnetic field, RF pulses and/or TVMF gradients are referred to in this disclosure as xe2x80x9cthe MRI environment.xe2x80x9d
Of the 18 million MRI scans done per year, approximately 10% of the patients are sedated during scanning for a variety of reasons. These patients are sedated using general, conscious intravenous (IV, spinal and epidural), orally administered (chewing tablets) or local anesthesia. If anesthesia is administered during MRI scanning, the law generally mandates that the patient""s vital signs be monitored continuously. Monitoring of different vital parameters depends on the patient condition such as heart patient, pediatric or claustrophobic and the type of anesthesia administered. In the past, the attending anesthesiologist made the decision. More recently, the American Society for Anesthesia has published guidelines describing both the physiological monitoring equipment and parameters that must be measured for different patient types (xe2x80x9cBoth sedated and critically III require Monitoring during MRIxe2x80x9d, Mark Schiebler, MD, et al. www.invivoresearch.com/topics/vital signs/survey.html) and White Paper on xe2x80x9cMRI Safetyxe2x80x9d, Charlotte Bell, MD, et al., American College of Radiology, AJR 2002; 178:1335-1347). According to these guidelines, the key parameters that must be continuously monitored include: EKG, Pulse Oximetry, Blood pressure, and Respiration by end tidal CO2/Capnograph or other methods.
Generally the three broad categories of problems are experienced when monitoring the vital signs of sedated patients in the MRI: 1) MRI environment induced interference in the vital sign monitoring equipment; 2) inadequate monitoring of respiration due to long separation between the patient and equipment producing latencies, and blockages in capnograph equipment lines; and 3) use of conventional ferrous-based EKG electrodes and lines cause burns to patients. Therefore the real time control is compromised.
Each of the above problems has been addressed in light of the monitoring equipment. Because the key-monitoring equipment used in detecting the vital signs in the MRI environment is the EKG, a brief interpretation of the EKG waveforms and problems associated with them during the scanning is provided below.
The electrocardiogram (EKG) measures changes in skin electrical voltage/potential caused by electrical currents generated by the myocardium. This electrical activity is typically represented by PQRST waveforms. The P wave reflects atrial depolarisation, while the QRS complex represents ventricular depolarisation, and the T wave ventricular repolarisation. Repolarisation is a process that occurs in many cells where the electrical potential across the cell membrane returns from the value during the action potential to that of the resting state (the resting membrane potential). Although the EKG shows heart rate and rhythm and can indicate myocardial damage, it does not directly give information on the adequacy of contraction. Normal electrical complexes can exist in the absence of cardiac output, a state known as pulseless electrical activity or electromechanical dissociation (EMD). The pulseless behavior is a special case of the myocardium but generally there is a direct correlation between the electrical activity as measured by the EKG with the mechanical activity as measured by phonocardiography. The foregoing is known to those skilled in the art and described in, xe2x80x9cPhonocardiography: Measurement of Heart Soundsxe2x80x9d, www.seas.smu.edu/xcx9ccd/EE5340/lect20/tsld011.htm, which is incorporated herein by reference in its entirety.
The EKG is generated using the 3, 5 or 12 lead configuration depending on the circumstances. For example in the MRI, usually 3 or 5 lead EKG is used because the patient is imaged while sedated but does not undergo surgery. At the end of each lead is an electrode that measures the small potential difference produced as a result of heart""s electrical activity. By measuring for example the Rate, Rhythm, Impulse Axis, Hypertrophy and Infarction, information about the heart condition can be determined. These characteristic parameters are determined from the data manifested in V1 through V6 leads placed on specific locations on the chest and 1, 2, 3, AVR, AVL and AVF leads placed on the limbs, etc. Normal and abnormal rate and rhythm EKG waveforms that could be used to monitor vital signs as well as to determine other heart conditions are known to those skilled in the art and described in the article xe2x80x9cNormal Sinus Rhythmxe2x80x9d, www.rchc.rush.edu/rmawebfiles/abnl%20rhythm%20for%20parent %20body.htm and www.rchc.rush.edu/rmawebfiles/EKG%20for%20parents%20body.htm, which are incorporated herein by reference in their entireties.
Using the empirically correlated data not only provides clinical information about the five aspects of the heart""s electrical activity but also provides variations that reflect other heart conditions associated within each of the five categories. It is well documented in the literature that the P wave signifies the generation of electrical impulses from the SA node, which travels down the AV node into the myocardial cells. The QRS complex represents the electrical impulse when it travels from the AV node into the Purkinje fibers into the myocardial cells and produces ventricular contractions. This signal can therefore provide information about the mechanical contraction of the heart""s ventricles, which is followed by its relaxation (process of repolarization). This characteristic signal when used by itself or in conjunction with other waveforms reveals many heart conditions such as arrhythmias, abnormal rates and infarctions; provided the EKG waveforms are not corrupted.
A number of manufacturers such as HP, Colin Medical etc. make vital sign monitoring systems that are frequently used in operating rooms and outpatient surgical environments. These systems provide continuous monitoring capability of the EKG, pulse oximetry, blood pressure, respiration rates via end-tidal CO2, etc. However, it has been observed that these monitors do not work well in the MRI environment. It is found that the EKG waveform is corrupted due to strong static magnetic fields, RF pulses, and the TVMF. For patients oriented in the supine position in the MRI scanner (Anesthesia Equipment in the MRI Suitexe2x80x9d, Charlotte Bell, MD and Rebecca Dubowy, MD, Department of Anesthesiology, Yale University School of Medicine, New Haven, Conn., USA. www.gasnet.org/mri/about/about-mri3_br.phb), the following effects are observed in the output EKG waveforms and the associated hardware:
1. The static magnetic field induces maximum voltage-charges in the conducting blood column within the transverse aorta since it is 90 degrees to the field (Peden, et.al. 1992 cited in xe2x80x9cAnesthesia Equipment in the MRI Suite, Charlotte Bell, MD and Rebecca Dubowy, MD, Departnent of Anesthesiology, Yale University School of Medicine, New Haven, Conn. USAxe2x80x9d). These charges are superimposed on the EKG waveform and are observed to be greatest in the ST segments and T waves in leads I, II, V1, V2 elevating the waveforms. The elevation of the waveforms increases with increasing magnetic field strength and can mimic EKG changes of myocardial injury.
2. Spike artifacts that mimic R waves of the EKG are produced when the magnetic field gradients are applied for imaging the tissue along with the RF pulses. These artifacts can simulate arrhythmias and produce an error in heart rate.
3. The pulsed RF field produces heating of the leads and electrodes (Catheters and Guide wires in interventional MRI: Problems and Solutions, M. K. Konings, et. al, Medica Mundi, 45/1 March 2001).
The first two effects corrupt the true EKG waveform and make it difficult to interpret the patient condition while the third effect causes skin bums. As a result, several MRI compatible EKG monitoring systems have been developed utilizing EKG electrodes and leads made of carbon graphite vs. the typical Ag/AgCl. The carbon graphite material is used to lower resistance at these RF frequencies and eliminate ferromagnetism so that the interference induced heating is minimized. Additionally, filters are used in the signal processing to minimize artifacts. Although using graphite electrodes, special filters, ensuring cable straightness, and placing towels on the patient""s chest minimizes the skin bums, the false R spikes, elevated ST segment and T waveforms are still manifested in the EKG when the magnetic field gradients and RF field are applied.
Other techniques such as Pulse Oximetry Plethysmography have been used as a heart tachometer (mechanical motion sensor), but they are not useful for ischemia or arrhythmia detection. They provide delayed response and are unable to discern all four heart sounds. Telemetry units have been used with low magnetic fields (0.6T), but generally interfere with the RF needed for imaging (Barnett, et. al. 1988, McArdle, et. al. 1986 cited in xe2x80x9cAnesthesia Equipment in the MRI Suitexe2x80x9d, Charlotte Bell, MD and Rebecca Dubowy, MD). Therefore, the presence of false R spikes, elevated ST segment and T waves give incorrect rates and rhythms, which leads to misinterpretations and misdiagnosis and makes it impossible to reliably detect ischemia or arrhythmias (ventricular or atrial flutter/fibrillation); the worst two life threatening conditions. Because presently there are no alternatives, for patients that are highly susceptible to ischemia and arrhythmias, a 12-lead EKG pre and post MRI scanning is recommended. If an unstable condition arises, the patient is removed from the magnetic field for proper EKG analysis and treatment, which is the common procedure as suggested by the MRI panel.
For respiration monitoring, the airway adapter based capnograph requires long tubes between the patient and the monitoring equipment. These not only get plugged due to patient mucous but also introduce unacceptable data latency and therefore cannot be used in reliably measuring respiration. To eliminate data latency, long tubes were replaced with fiber optic sensors that were mounted in the airway adapter and could replace the electrical sensors at the end of the tubes to directly measure the airflow. Optovent RR 9700 builds a fiber optic based device, which detects the respiration rate by measuring the flow of air via an airway adapter vs. chest wall movement using inductance plethysmography. Although this technology is immune to the MRI environment, it is insufficient to eliminate the adapter blockage. Additionally, adapter based sensors are invasive and are uncomfortable, producing logistical and control problems during the procedure.
Clearly EKG and airway adapter based technologies that are electrical in nature are insufficient and unreliable for detecting the vital signs (rate, rhythm and respiration) during MRI scans because of the presence of artifact spikes, elevated ST segments that corrupt the interpretation and delayed response with insufficient resolution. This greatly impedes the reliability of monitoring the vital signs especially in patients that are sedated or have heart conditions. Therefore, different technologies are required in the MRI environment that are neither electrical in nature nor are airway adapter based for the measurement of heart rate, rhythm, and respiration. Reliable data must be continuously processed from the uncorrupted R-Rxe2x80x2 intervals and the QRS characteristics for the myocardial information while a different method to measure respiration is required.
2. Background of Monitoring in Confined Care Facilities
A class of patients (usually but not exclusively elderly) are mostly confined to their beds or rooms for periods of time during their treatment or monitoring such as at elderly care facilities, nursing homes, hospice and convalescent homes, sanatoriums or insane asylums, centers for recovery from drug and alcohol abuse and related facilities (referred to herein as xe2x80x9cconfined care facilitiesxe2x80x9d). These patients require substantial or constant oversight to monitor their well-being and whereabouts within the facilities usually over the long term. Ideally, a nurse or other caregiver would attend the patient""s bedside at all times. However, it is generally impractical and uneconomical to provide this level of care at these facilities. Typically, a few staff personnel serve many patients periodically checking on the status of individual patients. Because the caregivers/staff are not constantly aware of the condition of each patient, serious problems can develop. A patient may leave their bed, either intentionally or accidentally. Even if intentional, the patient may take a fall or become disoriented without being able to timely press the emergency button to seek help. Dementia patients wander off from their rooms or the facility altogether making it difficult for the staff to determine their whereabouts. With only periodic visual checks by the staff and no capability to determine their whereabouts, the patient may be exposed to extended periods of physical and/or mental distress before being located and rendered help to prevent untimely deaths.
3. Background of Vital Sign Monitoring in Hospitals
Continuous and real-time measurement of human physiological parameters, such as respiration, heart rate, blood pressure and oxygenation, can be essential to the preservation of life in numerous clinical settings, including the operating rooms (OR) during procedural sedation, in intensive care units (ICU) and recovery rooms. Indeed, in most industrialized countries, law mandates real time continuous measurements of multiple physiological variables in a variety of clinical situations. Different types of instruments are used to monitor such variables depending on the clinical setting. For example, it is common to monitor heart rate using a 3 or 5 lead electrocardiogram (EKG), respiration rate by end-tidal (end-expiration) volume CO2, blood pressure with an invasive catheter or sphygmomanometer, and oxygenation with a pulse oximeter.
Unfortunately, several continuous monitors of physiological function (e.g., continuous blood pressure using an intra-arterial catheter and a transducer apparatus) are associated with considerable risk and/or extreme costs. For example, continuous measurement of arterial blood pressure requires a skilled physician to introduce a catheter into an artery, while complications include necrosis of the limb, and systemic life-threatening infections. As there is presently no suitable non-invasive alternative, more than one million intra-arterial catheters are placed per year. Another example, pulmonary artery catheters, are introduced directly into the heart and may cause sepsis, ventricular dysrhythmias, and pulmonary artery rupture, all of which are associated with a very high mortality. Indeed, there are an estimated 100,000 cases of catheter-related sepsis and death per year in the U.S. alone. Like intra-arterial catheters, approximately one million pulmonary artery catheters are used annually, at a cost exceeding $1000 per patient, due to lack of a low-risk alternative.
Blood pressure (BP) is a parameter of utmost importance that cannot be measured continuously, non-invasively (NI) and accurately. Because of the potential threat of complications, risk to the patient and extreme costs involved, physicians must compromise on the choice of monitoring selected. They either settle for measuring blood pressure non-invasively on periodic intervals, accepting that the procedure gives discomfort to the patient and is not continuous, or choose the invasive approach if conditions warrant such utilization. If a non-invasive method is chosen, the measurement is generally performed using the xe2x80x9causcultatory/oscillometric inflation techniquexe2x80x9d which is regarded as the xe2x80x9cGold Standardxe2x80x9d worldwide. The instrument used is either the manually operated xe2x80x9ccuff and puffxe2x80x9d sphygmomanometer or an automatic one. The automatic versions of these instruments provide blood pressure data on a periodic cycle but not continuously. The periodic cycle is programmable by the user from 1 minute to 8 hours or more. These instruments used are considered non-ideal for the following reasons: 1) BP cannot be measured continuously; 2) the patient experiences discomfort due to frequent squeezing of the arm to occlude blood flow and 3) false alarms or erroneous data are produced due to patient motion induced artifacts. These problems greatly interfere with the sleep/rest cycles especially during recovery or after sedation or at nighttime in an intensive care unit.
Other instruments, such as developed by COLIN-Europe for continuous NIBP monitoring, use several point sensors in a cuff configuration that are piezoelectric in nature. The piezoelectric sensors output electrical signals in response to mechanical movements such as that produced by the arterial wall. These devices have the following disadvantages: 1) the sensors are not passive and therefore cannot be used in environments such as the Magnetic Resonance Imaging (MRI) and Computer Tomography (CT) scan because they are affected by Electromagnetic interference (EMI), magnetic fields and Radio Frequencies (RF); 2) they generate erroneous data because the piezoelectric sensors are sensitive to mechanical shocks; and 3) they need to be continually aligned with the arterial wall, and calibrated frequently since they are not distributed area sensors.
1. Use of Fiber Optic Interferometric Vital Sign Monitor in MRI Environment
The fiber optic sensor of the present invention discussed in detail below, measures the acousto-mechanical activity when the fiber is placed in close proximity with the body, in particular the myocardium sounds (S1, S2, S3 and S4) and the respiration rates simultaneously. Heart and respiration rates of a patient are two vital sign parameters that must be detected reliably during MRI scanning. A single or plurality of the inventive sensors may be used for listening to both the normal and abnormal heart sounds (S1, S2, S3 and S4) in addition to detecting the respiration rate. Because the first heart sound represents the closure of both the mitral and tricuspid valves and also represents the initiation of ventricular contraction or systole, it is generated within tens of milli-seconds after the EKG""s QRS complex and can be used to determine the heart rate. In the same way, the S2 sound represents the closure of both the aortic and pulmonary valves and represents also the initiation of the ventricular relaxation or diastole occurring at the same time as the T wave in the EKG. Because the S1 sound is strong, it can be used to measure the heart rate more accurately than with the EKG. Absence of S1 sound or abnormal sound would suggest heart problems. In such a case, the patient may be removed from the MRI, an EKG administered without the magnetic fields along with life saving CPR etc. Therefore, in one embodiment, multiple optical sensors may be affixed to the patient""s chest around the apex, atria and ventricles to measure the heart sounds/rate, which is facilitated by a microprocessor based counter and recorder.
The inventive fiber optic sensor may also be used to supplement the EKG information by reprocessing corrupted data. For example, multiple optical sensors and graphite electrodes (optrodes) may be packaged together and simultaneously affixed to the patient""s chest at the atria, apex and ventricles similar to when recording an EKG. The output signals from both the optical sensor and EKG electrodes are then correlated and processed to eliminate unwanted spikes and the elevated ST segment and T wave from the EKG waveforms. Different schemes to process these signals may be used such as fast Fourier transforms or time correlation filtering techniques to process the data.
The inventive fiber optic interferometric sensors may also be combined with other sensors used in MRI to monitor sedated patients. These sensors include the following: optical pulse oximetry to measure partial pressure of oxygen or heart beat; non-invasive and invasive blood pressure sensors; capnographs or end-tidal volume CO2 for respiration measurements; and temperature measurements.
The inventive fiber optic sensors may be configured in a jacket or mattress pad to monitor the vital signs non-invasively as described below. These could be combined with the EKG and other monitoring devices for compensating data.
2. Use of Fiber Optic Interfermetric Vital Sign Monitor in Confined Care Facilities
In confined care facilities; the inventive fiber optic vital sign monitor described below may be used to provide a means of immediate notification to the staff when a patient has left their bed. Of course, a patient doesn""t have to leave bed to experience difficulties that require immediate attention from the staff. Accordingly, the fiber optic monitor can also provide immediate notification to the staff when there is a significant deviation in either their breathing or the heart rate from normal. In situations when a patient may have left the bed, the inventive fiber optic sensor, when supplemented with an RF or IR transmitter device, may provide the whereabouts of the patient within the facility and sound an alarm in certain cases.
These and other objects are achieved by this aspect of the invention, which employs a combination of the passive inventive fiber-optic interferometer sensor system and an RF or IR transmitter that is issued to the patient on checking into the facility. The fiber optic sensor system continuously monitors the patient""s vital signs (including heart and breath rate) and provides immediate notification to the staff in case either rate goes outside of prescribed bounds, or in case the patient leaves the bed and the rate signals are lost, whereas the RF or IR transmitter emits a patient Identification (ID) code that is picked up by RF receivers installed in the room, bathroom and hallways to determine their whereabouts.
A sensor pad comprises the optical fiber that responds to acousto-mechanical movements of the patient. No connections (wires, fibers, or tubes) to the patient are necessary. The patient merely lies on the bed and the sensor pad responds to the micro-movements caused by the patient""s heartbeat and breathing. Two optical fibers packaged in a single cable emerge from the sensing pad and connect to a Fiber Optic Signal Conditioning Box. The box includes the following: a light source that sends light through the fiber coil in the sensing pad; a detector that converts the light that has traveled through the sensing coil into an electrical signal; a processor that extracts the breath rate and heart rate from the modulation of the detectors signal; an interface communication module located in the signal conditioning box that sends the results to the local and/or central/monitoring station to provide numeric readouts and alarms; the vital sign signals may be transmitted over exiting power lines, wireless radio link or new phone lines, cable lines, local area network lines.
A battery operated short range RF or IR transmitter cuff emits the patients ID periodically at preset intervals. This cuff is placed on the patient""s wrist or leg, for example. The code is unique and is emitted in serial time segments in such a way that there are no message collisions between the IDs of various patients within the facility resulting in data washout at the receiver. Short-range RF or IR receivers located within the bedroom, bathroom and hallways pick up these unique signals. Because the range of these receivers is limited, the presence of a signal indicates the proximity of the patient. The receivers perform the following functions: they detect and process each patient""s ID code; an interface communication module in the receiver transmits the message consisting of the processed ID codes and location of each patient to the central monitoring station; the messages may be transmitted over exiting power lines, wireless radio link or new phone lines, cable lines, local area network lines.
At the central monitoring station, information about the patient is generated using both the vital sign and the RF or IR signals that have been processed using a signal processor. This information for each patient can be provided as follows: a graphical display of the breath rate; a numeric display of the breath rate; a graphical display of the heart rate; a numeric display of the heart rate; a numeric display of the patient""s location within the facility or visual display such as a point representing in real time the location of the patient on a graphical map of the facility.
Different alarms are communicated, in the form of a text message, a flashing light, an audible signal, or any combination. All or any portion of the above information set may be displayed/output at either the local or the remote Readout Interface. The location of the local readout interface may be in the patient""s room.
Different communication links are established for each patient within the Confined Care Facility to communicate the heart and breath rate outputs of the Fiber Optic Monitor to the Central Station from the local readout. In addition, the RF or IR Receiver output that detects the location of the patient within the room, bathroom or hallways is provided to the Central Station.
3. Use of Fiber Optic Vital Sign Monitor in Hospitals
Considering the problems described regarding vital sign monitoring in hospitals, there is clearly a need for better instruments that can provide blood pressure (BP) and other physiological functions non-invasively, continuously and accurately. Therefore, one of the primary objectives of this embodiment of the current invention is to provide non-invasive monitoring of BP with continuous readouts using minimal squeeze pressure that ensures comfort to the patient. It is yet another objective of the invention to provide a continuous readout of the patient""s heart rate along with BP, and provide alarm notification if the levels deviate from prescribed bounds. A secondary objective of the invention is to provide features such as the following: automatic alarm notification if the BP level exceeds the prescribed bounds; a threshold that releases air pressure in case the system malfunctions; and built in test (BIT) for fault detection, and visual or audio indications for proper operation and any malfunctions.
These and other objects of this aspect of the present invention are achieved using the all-passive fiber-optic sensor based on optical interferometer, which is described below. Because the fiber optic sensor responds to acousto-mechanical signals, it can be used to continuously and non-invasively monitor patient""s blood pressure, heart rate and respiratory rate. One aspect of the invention is on the use of a single sensor in measuring two of the three functions; namely the blood pressure and the heart rate. The system consists of the following: inflatable cuff with integrated fiber optic sensor; controls and signal conditioning unit; central monitoring station, and communication link.
A cuff is used to measure both the blood pressure and heart rate non-invasively and continuously. The cuff may be inflated or deflated using an air pump that is located outside the cuff in the controls unit. The fiber optic sensor is integrated within the cuff in such a way that they can be wrapped lightly around the patient""s arm or leg with a preload that is required to detect pulsation of the arterial wall. High sensitivity, distributed area sensing and immunity to EMI, RFI, etc. are some of the key advantages offered by the fiber optic sensor of this aspect of the present invention. Airlines may be employed for inflating or deflating the cuff using a microprocessor driven servo control pump system that is located in the controls unit.
The Controls and Signal-Conditioning unit includes various elements one of which is an LED that sends light through an input fiber optic lead into the sensor located in the sensing cuff. A detector converts the light returned from the sensor into electrical signals via a second fiber optic lead. A servo control pressure system actively monitors and regulates the hold down pressure in the cuff. A microprocessor provides automatic calibration of the system, initiates the step sequence command to determine optimum hold down pressure, applies algorithms for noise minimization and drift control, conducts built in test, and provides safety pressure threshold limits, blood pressure and heart rate data storage, processing, and manipulation. The Controls and Signal-Conditioning unit provides local numeric and graphical displays and alarms. A keypad is used through which a user can interface with the system for set up and calibration. A communication link module sends the data to the local and/or central monitoring station to provide numeric readouts and alarms. The link could be over existing power lines, a wireless radio, existing or new phone lines, cable lines, and local area network lines.
At the central monitoring station, information about each patient is recorded and reported to the staff. The following information as a minimum can be provided for each patient: a graphical display of the blood pressure vs. time; a numeric display of the current blood pressure reading; a graphical display of the heart rate; a numeric display of the heart rate.
Different alarms may be provided, which can be in the form of a text message, a flashing light, an audible signal, or any combination. All or any portion of the above information set can be displayed/output at either the local or the remote Readout Interface.
Multiple patients monitored by a single remote readout station may be located at the staff desk typically within the same room. Results from the individual patients can be communicated to the central station using standard communication protocols such as RS485, and Ethernet that allow a single receiving station to monitor multiple sources. The communication can be over copper wires, optical fibers or wireless or in any other manner discussed herein.